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regl-audio

Tools for working with audio in regl. This module has the following components:

  • An analyser
  • A microphone connection

Examples:

Examples

Here is a simple beat detector:

const regl = require('regl')()

const drawBeats = regl({
  vert: `
  precision highp float;

  attribute vec2 position;
  varying vec2 uv;

  void main () {
    uv = position;
    gl_Position = vec4(position, 0, 1);
  }
  `,

  frag: `
  precision highp float;

  varying vec2 uv;

  uniform float beats[16];

  void main () {
    float intensity = 0.0;

    float bin = floor(8.0 * (1.0 + uv.x));

    for (int i = 0; i < 16; ++i) {
      if (abs(float(i) - bin) < 0.25) {
        intensity += step(0.25 * abs(uv.y), beats[i]);
      }
    }
    gl_FragColor = vec4(intensity, 0, 0, 1);
  }
  `,

  attributes: {
    position: [
      -4, 0,
      4, 4,
      4, -4
    ]
  },

  count: 3
})

require('regl-audio/microphone')({
  regl,
  beats: 16,
  name: '',
  done: (microphone) => {
    regl.frame(() => {
      microphone(({beats}) => {
        drawBeats()
      })
    })
  }
})

regl-audio/analyser

This module takes a WebAudio analyser node and returns a scope command giving convenient access to stats from the analyser.

  • PCM time domain data
  • STFT frequency domain data
  • Beats
  • Pitch

API

const audio = require('regl-audio/analyser')(options)

The constructor for the analyser takes the following arguments:

Parameter Description Default
regl A handle to a regl instance Required
analyser A WebAudio analyser node Required
name A prefix for the analyser output. ''
sampleRate The sample rate of the audio source in Hz 44100
beats The number of beats to detect grouped by pitch 16
beatTime Duration of moving average for beats in seconds 1
beatThreshold Cutoff for beat detection (must be between 0.5 and 1) 0.8
pitches Number of pitches to detect 4
maxPitch Maximum detectable pitch in Hz 10000
pitchTime Duration of moving average for pitch in seconds 0.25

audio(block)

The result is a regl scope command with the following properties:

Context Description
sampleCount Number of samples
freq Array of frequencies
time Array of PCM time samples
cepstrum The cepstrum of the signal
timeTexture Current time information in texture
freqTexture Current frequency information in texture
volume Volume of the current signal
beats Array of detected beats sorted from low to high pitch. Each beat is a scalar in [0, 1]
pitches Array of detected pitches sorted from loudest to softest in Hz
Uniform Type Description
sampleCount float Number of samples in texture
time sampler2D A sampler storing the PCM time data
freq sampler2D A sampler storing the frequency data
volume float Volume of the signal
beats float[NUM_PITCHES] An array of beats
pitches float[NUM_PITCHES] The array of detected pitches

Note that these context variables are optionally prefixed depending on the name parameter.

regl-audio/microphone

A short cut which gives you an analyser node connected to the microphone input from the computer. Note that this must be run on a secure domain.

API

const mic = require('regl-audio/microphone')(options)

The options are the same as above, except that it takes a webaudio context via the options.audioContext parameter instead of an analyser node. By default everything is prefixed with mic_ though this can be changed by passing some alternative to name.

License

(c) 2016 Mikola Lysenko. MIT License

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Audio helper toolbox for regl

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